PB1826: CELLULAR AND MOLECULAR CHARACTERIZATION OF THE ANTINEOPLASTIC EFFECTS OF CEPHALOCHROMIN IN MODELS OF ACUTE MYELOID LEUKEMIA
Authors: Mariane Cristina Do Nascimento, Diego A Pereira-Martins, Guilherme Augusto Sousa Alcântara, Keli Lima, Hugo Passos Vicari, Marcelo José Pena Ferreira, Leticia Leticia Veras Costa-Lotufo, João Agostinho Machado Neto, Eduardo Magalhães Rego
Journal: HemaSphere (2023)

Topic: 3. Acute myeloid leukemia - Biology & Translational Research Background: Usually, the use of cytarabine plus daunorubicin (7 + 3) has been the international treatment standard protocol for acute myeloid leukemia (AML) patients in the last 4 decades. Unfortunately, elderly patients, which represent the majority of AML pacients, are usually unable to tolerate this intensive chemotherapy protocol, being also not eligible for bone marrow transplantation. Venetoclax is a BCL-2 inhibitor indicated for the treatment of patients with AML who are not eligible for intensive therapy, however, 40% of the treated patients will evolve with resistance. Therefore, there is a clear need to identify new antileukemic agents. Cephalochromin is a compound derived from the fungi Cosmopora vilior, that exhibited pro-apoptotic effects and inhibition of cell growth in lung cancer cells. In this model, cephalochromin induces inhibition of cell proliferation through induction of apoptosis, mitochondrial damage and autophagy, having among its molecular targets the cell cycle controllers like cyclins and survivin (BIRC5). Aims: To evaluate the effects of cephalochromin on cell proliferation and survival using several cellular models of AML and to evaluate the combined effects of cephalochromin with venetoclax. Methods: Concentration-response cytotoxicity curves analyzed by MTT assay for venetoclax and cephalochromin in 12 AML cell lines (HEL, HL-60, Kasumi-1, KU812, K-562, MOLM-13, MV4-11, NB4, OCI-AML3, SET-2, THP-1, and U-937) treated with graded concentrations of venetoclax and cephalochromin (0.000128; 0.0064; 0.032; 0.16; 0. 8; 4 and 20 μM) for 72 hours. Results: Twelve different AML cell lines types were tested with cephalochromin and IC50 values ranged from 0.45 to >20 µM. Analysis of cephalochromin cytotoxicity in healthy peripheral blood mononuclear cells revealed IC50 values ranging from from 3.7 to 8.8 µM for cephalochromin, suggesting a potentially favorable therapeutic window. Evaluation of venetoclax cytotoxicity in the same models revealed three cell models if significant resistance to venetoclax therapy, being Kasumi-1 and U-937 cells having partially resistance and OCI-AML3 cells as being highly resistant. Cephalochromin induced apoptosis in a concentration-dependent manner in all tested leukemic models. Our cell cycle analysis revealed a progressive increase in subG1 fraction upon treatment with cephalochromin, which was better evidenced in Kasumi-1 cells. In OCI-AML3 cells (a notorious model for venetoclax-resistance in AML), low concentrations of venetoclax (5 µM) and cephalochromin (2.5 µM) combined showed apoptosis induction in more than 95% of the cells. Similar results were observed for U-937 with low concentrations of venetoclax (2.5 µM) and cephalochromin (2,5 µM) and Kasumi-1 cells (venetoclax: 0,6 µM and cephalochromin: 2.5 µM). Molecularly, treatment with cephalochromin increased PARP1 cleavage and γH2AX levels in all evaluated models. We observed a reduction of MCL1, a BCL2 family protein associated with venetoclax resistance in Kasumi-1 cells upon cephalochromin therapy. Reduced SQSTM1/p62 levels in U-937 and Kasumi-1 cells, suggested induction of autophagy, corroborating with previous literature data, which suggested cephalochromin as an autophagy inducer in cancer cells. Summary/Conclusion: Our data suggest that cephalochromin reduces cell viability in a concentration- and time-dependent manner in cellular models of AML, associated with reduced clonogenicity. Cephalochromin treatment induces apoptosis and it has synergistic effects on venetoclax-induced apoptosis, possibly due to induction of autophagy and DNA damage. Keywords: Acute myeloid leukemia